KAINE: I would be open to a proposal that would have some minimum tax level for everyone. But I do insist, many of the 47 percent that Gov. Romney was going after pay a higher percentage of their taxes than he does.

In an ad released Wednesday, Kaine broke with President Obama’s proposed tax policy of increasing the tax rate on income over the $250,000 threshold to Clinton-era levels.

"President Obama wants the Bush tax cuts to expire for people earning over $250,000; George Allen wants to make all the tax cuts permanent," Kaine says in the ad. "There’s a middle ground. Let the tax cuts expire for those earning over $500,000."

The position is not new, however. Kaine argued in April for the $500,000 mark, and against the "Buffett Rule," which would have applied a minimum 30 percent rate on individuals who earn more than $1 million in income.